A product or process designated as a hybrid typically refers to something with two or more unlike features. In the context of vehicles, the term hybrid is typically used to refer to a vehicle that has two or more means or modes for providing movement. For example, one means or mode might comprise an internal combustion engine and the other means or mode might comprise an engine or motor operating from a different power source or utilizing a different fuel. That different power source may be such as electricity.
Off-highway vehicles lend themselves to hybrid technology. These vehicles include, but are not limited to working vehicles such as those used in construction, agriculture, mining, forestry, material handling, specialty chassis, outdoor power equipment, leisure/utility vehicles, and those used in various industrial markets.
As can be appreciated by the foregoing list of vehicles, off-highway vehicles are often required to be robustly constructed vehicles that must be capable of working in nontraditional environments and/or nontraditional conditions. However, prior hybridized off-highway vehicles using a torque converter are known to have specific constraints that can be exacerbated by these environments, conditions and vehicle layout/design.
By way of example, one constraint of torque converters is that they cannot be efficiently driven in the reverse direction. In other words, when power is provided to the torque converter from the turbine side of the converter, the converter does not operate as efficiently as when power is provided from the impeller side. Examples such as these are exacerbated by environments, conditions and vehicle layouts, where room to operate a vehicle can be very tight and/or where there is a danger of explosion.
Known hybridized off-highway vehicles connect an electric device directly to the engine, typically between the engine and the transmission. The drawback with this design is that additional space is needed in the already tight engine compartment for the electric device. Additionally, as the transmission is moved further from the engine to accommodate the electric device, it can interfere with parts of the chassis.
Other solutions connect the electric device to the transmission output. Since the spread on speed is quite large (because of the number of gears), dimensioning an electric device at this location is difficult since it must combine very high torque at very low speeds with high speeds.
The present invention, described more fully below, overcomes the limitations associated with the known hybrid technologies and employs, by way of example only, it in an off-highway vehicle.